Short-circuit pinpointing device

ABSTRACT

A short-circuit pinpointing device for testing a wide-range air/fuel sensor includes a current-sink and a controller. The current-sink is selectively connectable to one or more of sensor-terminals of a wide-range air/fuel sensor that include a reference-terminal, a pump-terminal, a return-terminal, and a tag-terminal. The controller is in communication with the current-sink and the sensor-terminals. The controller controls the connection of the current-sink to the one or more sensor-terminals. The controller also determines one or more status-values based on signals present at the sensor-terminals. The controller also determines a sensor-status of the wide-range air/fuel sensor based on the connection of the current-sink and the one or more status-values.

TECHNICAL FIELD OF INVENTION

This disclosure generally relates to a short-circuit pinpointing device,and more particularly relates to a short-circuit pinpointing device fortesting a wide-range air-fuel sensor.

BACKGROUND OF INVENTION

It is desirable to diagnose a short-circuit to a battery and/or a groundof an air-fuel sensor in an automotive application. A wide-rangeair-fuel sensor typically has several electrical wires that may becomeshort-circuited to the battery or ground. Difficulty in determiningwhich sensor wire is short-circuited may be caused by the internal cellbias voltage from the reference and pump cells, battery and groundvoltage fluctuations, and large common-mode signals. Additionally, it isadvantageous to be able to pinpoint a short-circuit while the sensor isat operating temperature, of which the prior art is incapable.

SUMMARY OF THE INVENTION

In accordance with one embodiment, a short-circuit pinpointing devicefor testing a wide-range air/fuel sensor is provided. The short-circuitpinpointing device includes a current-sink and a controller. Thecurrent-sink is selectively connectable to one or more ofsensor-terminals of the wide-range air/fuel sensor that include areference-terminal, a pump-terminal, a return-terminal, and atag-terminal. The controller is in communication with the current-sinkand the sensor-terminals. The controller controls the connection of thecurrent-sink to the one or more sensor-terminals. The controller alsodetermines one or more status-values based on signals present at thesensor-terminals. The controller also determines a sensor-status of thewide-range air/fuel sensor based on the connection of the current-sinkand the one or more status-values.

Further features and advantages will appear more clearly on a reading ofthe following detailed description of the preferred embodiment, which isgiven by way of non-limiting example only and with reference to theaccompanying drawings.

BRIEF DESCRIPTION OF DRAWINGS

The present invention will now be described, by way of example withreference to the accompanying drawings, in which:

FIG. 1 is an illustration of a short-circuit pinpointing device inaccordance with a first embodiment;

FIG. 2 is an illustration of a controller for the short-circuitpinpointing device of FIG. 1 in accordance with the invention;

FIG. 3 is a table that summarizes a test-result logic versus asensor-status in accordance with the invention;

FIG. 4 is an illustration of a short-circuit pinpointing device inaccordance with a second embodiment;

FIG. 5 is a flow chart illustrating a logic used by the controller inaccordance with the invention;

FIG. 6 is an illustration of a short-circuit pinpointing device inaccordance with a third embodiment; and

FIG. 7 is an illustration of a short-circuit pinpointing device inaccordance with a fourth embodiment.

DETAILED DESCRIPTION

FIG. 1 illustrates a non-limiting example of a first embodiment of ashort-circuit pinpointing device 10, hereafter referred to as the device10, that is designed to test a wide-range air/fuel sensor 12(WRAF-sensor 12) to detect various short-to-ground and short-to-batteryconditions. The device 10 includes input-channels 14 for connecting tothe WRAF-sensor 12 at a reference-terminal 16, a pump-terminal 18, areturn-terminal 20, and a tag-terminal 22. The WRAF-sensor 12 mayinclude an additional ground-terminal (not shown) as will be recognizedby those in the art.

The device 10 also includes a current-sink 24 that is selectivelyconnectable to one or more of the WRAF-sensor 12 terminals describedabove. The current-sink 24 may be any current-sink 24 suitable for usein an automotive application and may produce an electrical current inthe range of 400 micro-amps (μA) to 600 μA. While FIG. 1 illustratesmultiple current-sinks attached to the WRAF-sensor 12 terminals, it willbe recognized by those in the art that a single current-sink 24 may beused with multiple switching-devices attached to the WRAF-sensor 12terminals.

The device 10 also includes a controller 26 in communication with thecurrent-sink 24 and the WRAF-sensor 12 terminals. The controller 26 maycontrol the connection of the current-sink 24 to the one or moresensor-terminals to determine one or more status-values 28 (FIG. 2) ofthe WRAF-sensor 12 based on signals present at the sensor-terminals. Thecontroller 26 may also determine a sensor-status 30 (FIG. 2) of theWRAF-sensor 12 based on the connection of the current-sink 24 and theone or more status-values 28, as will be described in more detail below.

The controller 26 may include a processor (not shown) such as amicroprocessor or other control circuitry such as analog and/or digitalcontrol circuitry including an application specific integrated circuit(ASIC) for processing data as should be evident to those in the art. Thecontroller 26 may include memory, including non-volatile memory, such aselectrically erasable programmable read-only memory (EEPROM) for storingone or more routines, threshold-values, and captured data. The one ormore routines may be executed by the processor to perform steps fordetermining if signals received by the controller 26 indicate thepresence of short-circuits as described herein.

The controller 26 may determine a first-value 32 based on a differencebetween signals at the reference-terminal 16 and the return-terminal 20while the current-sink 24 is disconnected as indicated by the openswitch S_ref (FIG. 1). The controller may then close switch S_refconnecting the current-sink 24 to the reference-terminal 16 and maydetermine a second-value 34 based on a difference between signals at thereference-terminal 16 and the return-terminal 20. It will be recognizedby one skilled in the art that the two switches connecting afirst-amplifier 36 to the reference-terminal 16 and the return-terminal20, and the switch connected to the output of the first-amplifier 36,are closed by the controller 26 in order to determine the first-value 32and the second-value 34. The controller 26 may then determine areference-error 38 based on the difference between the second-value 34and the first-value 32, and may store a first-result 70 as a logical ‘1’when a reference-threshold 40 is greater than the reference-error 38.The controller may also store the first-result 70 as a logical ‘0’ whenthe reference-threshold 40 is not greater than the reference-error 38.

The device 10 may also include three test-resistors that are eachselectively connectable between two of the sensor-terminals, wherein thecontroller controls the connection of the test-resistor between the twosensor-terminals, as illustrated in FIG. 1. A first-test-resistor 42 maybe connected between the reference-terminal 16 and the return-terminal20, a second-test-resistor 44 may be connected between thereturn-terminal 20 and the pump-terminal 18, and a third-test-resistor46 may be connected between the pump-terminal 18 and the tag-terminal 22while the first-value 32 and the second-value 34 are determined. Thethree test-resistors may be any resistor suitable for use in anautomotive application and preferably each have a resistance of1000-ohms.

The controller 26 may also determine a third-value 48 based on adifference between signals at the pump-terminal 18 and thereturn-terminal 20 while the current-sink 24 is disconnected asindicated by the open switch S_pump. The controller may then closeswitch S_pump connecting the current-sink 24 to the pump-terminal 18 andmay determine a fourth-value 50 based on a difference between signals atthe pump-terminal 18 and the return-terminal 20. It will be recognizedby one skilled in the art that the two switches connecting asecond-amplifier 52 to the return-terminal 20 and the pump-terminal 18,and the switch connected to the output of the second-amplifier 52, areclosed by the controller 26 in order to determine the third-value 48 andthe fourth-value 50. The controller 26 may then determine a pump-error54 based on the difference between the fourth-value 50 and thethird-value 48, and may store a second-result 72 as a logical ‘1’ when apump-threshold 56 is greater than the pump-error 54. The controller mayalso store the second-result 72 as a logical ‘0’ when the pump-threshold56 is not greater than the pump-error 54.

While the third-value 48 and the fourth-value 50 are determined by thecontroller 26, the first-test-resistor 42 may not be connected betweenthe reference-terminal 16 and the return-terminal 20, thesecond-test-resistor 44 may be connected between the return-terminal 20and the pump-terminal 18, and the third-test-resistor 46 may beconnected between the pump-terminal 18 and the tag-terminal 22.

The controller 26 may also determine a fifth-value 58 based on adifference between signals at the tag-terminal 22 and the pump-terminal18 while the current-sink 24 is disconnected as indicated by the openswitch S_tag. The controller 26 may then close switch S_tag connectingthe current-sink 24 to the tag-terminal 22 and may determine asixth-value 60 based on a difference between signals at the tag-terminal22 and the pump-terminal 18. It will be recognized by one skilled in theart that the two switches connecting a third-amplifier 62 to thepump-terminal 18 and the tag-terminal 22, and the switch connected tothe output of the third-amplifier 62, are closed by the controller 26 inorder to determine the fifth-value 58 and the sixth-value 60. Thecontroller 26 may then determine a tag-error 64 based on the differencebetween the sixth-value 60 and the fifth-value 58, and may store athird-result 74 as a logical ‘1’ when a tag-threshold 66 is greater thanthe tag-error 64. The controller 26 may also store the third-result 74as a logical ‘0’ when the tag-threshold 66 is not greater than thetag-error 64.

While the fifth-value 58 and the sixth-value 60 are determined by thecontroller 26, the first-test-resistor 42 may not be connected betweenthe reference-terminal 16 and the return-terminal 20, thesecond-test-resistor 44 may be connected between the return-terminal 20and the pump-terminal 18, and the third-test-resistor 46 may beconnected between the pump-terminal 18 and the tag-terminal 22.

If the stored test-results are such that the first-result 70 is logical‘1’, the second-result 72 is logical ‘0’, and the third-result 74 islogical ‘0’, then the controller 26 assigns a sensor-status 30indicative of a short-circuit on the reference-terminal 16. If thestored test-results are such that the first-result 70 is logical ‘0’,the second-result 72 is logical ‘1’, and the third-result 74 is logical‘0’, then the controller 26 assigns a sensor-status 30 indicative of ashort-circuit on the pump-terminal 18. If the stored test-results aresuch that the first-result 70 is logical ‘0’, the second-result 72 islogical ‘0’, and the third-result 74 is logical ‘1’, then the controller26 assigns a sensor-status 30 indicative of a short-circuit on thetag-terminal 22. If the stored test-results are such that thefirst-result 70 is logical ‘0’, the second-result 72 is logical ‘0’, andthe third-result 74 is logical ‘0’, then the controller 26 assigns asensor-status 30 indicative of a short-circuit on the return-terminal20. FIG. 3 is a table that summarizes test-result logic versus thesensor-status 30 that is performed by the controller 26.

It will be recognized by one skilled in the art that the determinationof the status-values 28 described above may be performed by thecontroller 26 independently and in any order.

The three amplifiers shown in FIG. 1 are for illustration purposes only.One skilled in the art will recognize that the three amplifiers may bereplaced by one amplifier by using multiple switching-devices to connectthe amplifier to the desired sensor-terminals as determined by thecontroller 26, as illustrated in FIG. 4.

FIG. 4 illustrates a non-limiting example of a second embodiment of thedevice 10 that may be used to pinpoint short-circuits in the WRAF-sensor12. It will be understood by those in the art that the controller 26 maycontrol the various switches and transistors to perform the testsdescribed herein.

The switches used to connect the current-sink 24, the amplifiers, andthe test-resistors may be any switches suitable for use in an automotiveapplication, and may include, but are not limited to, relays,thyristors, and transistors, as will be recognized by one skilled in theart of electronics.

FIG. 5 illustrates a flow-chart of a logic used by the controller 26 todetermine the various status-values 28 and the sensor-status 30 asdescribed above.

FIG. 6 illustrates a non-limiting example of a third embodiment of thedevice 10 that is designed to test another WRAF-sensor 12 to detectvarious short-to-ground and short-to-battery conditions. The device 10includes input-channels 14 for connecting to the WRAF-sensor 12 at areference-terminal 16, a pump-terminal 18, and a return-terminal 20. Thetable shown at the bottom of the drawing may be performed by software orother logic inside the controller 26.

FIG. 7 illustrates a non-limiting example of a fourth embodiment of thedevice 10 that is designed to test yet another WRAF-sensor 12 to detectvarious short-to-ground and short-to-battery conditions. The device 10includes input-channels 14 for connecting to the WRAF-sensor 12 at apump-terminal 18 and a return-terminal 20. The table shown at the bottomof the drawing may be performed by software or other logic inside thecontroller 26.

Accordingly, a short-circuit pinpointing device 10, and a controller 26for the short-circuit pinpointing device 10 is provided. The device 10enables the reliable and accurate determination of the location of theshort-circuit at any sensor-terminal using one electronic circuit overall the sensors' operating temperatures. The circuit is immune to anyabsolute circuit imperfection and non-idealities. Further, any componentmismatches and all other errors at the input sensing stage are cancelledand do not affect the integrity of the pinpointing function.

While this invention has been described in terms of the preferredembodiments thereof, it is not intended to be so limited, but ratheronly to the extent set forth in the claims that follow. Moreover, theuse of the terms first, second, upper, lower, etc. does not denote anyorder of importance, location, or orientation, but rather the termsfirst, second, etc. are used to distinguish one element from another.Furthermore, the use of the terms a, an, etc. do not denote a limitationof quantity, but rather denote the presence of at least one of thereferenced items.

We claim:
 1. A short-circuit pinpointing device for testing a wide-rangeair/fuel sensor, said device comprising: a current-sink that isselectively connectable to one or more of sensor-terminals of awide-range air/fuel sensor that include a reference-terminal, apump-terminal, a return-terminal, and a tag-terminal; and a controllerin communication with the current-sink and the sensor-terminals, whereinthe controller controls a connection of the current-sink to the one ormore sensor-terminals, determines one or more status-values based onsignals present at the sensor-terminals, and determines a sensor-statusof the wide-range air/fuel sensor based on the connection of thecurrent-sink and the one or more status-values.
 2. The device inaccordance with claim 1, wherein the controller determines a first-valuebased on a difference between signals at the reference-terminal and thereturn-terminal while the current-sink is disconnected, determines asecond-value based on the difference between signals at thereference-terminal and the return-terminal while the current-sink isconnected to the reference-terminal, determines a reference-error basedon the difference between the second-value and the first-value, anddetermines that a short-circuit is present on the reference-terminalwhen a reference-threshold is greater than the reference-error.
 3. Thedevice in accordance with claim 2, wherein the device includes threetest-resistors that are each selectively connectable between two of thesensor-terminals, wherein the controller controls the connection of thetest-resistor between the two sensor-terminals.
 4. The device inaccordance with claim 3, wherein a first-test-resistor is connectedbetween the reference-terminal and the return-terminal, asecond-test-resistor is connected between the return-terminal and thepump-terminal, and a third-test-resistor is connected between thepump-terminal and the tag-terminal.
 5. The device in accordance withclaim 1, wherein the controller determines a third-value based on adifference between signals at the pump-terminal and the return-terminalwhile the current-sink is disconnected, determines a fourth-value basedon the difference between signals at the pump-terminal and thereturn-terminal while the current-sink is connected to thepump-terminal, determines a pump-error based on the difference betweenthe fourth-value and the third-value, and determines that ashort-circuit is present on the pump-terminal when a pump-threshold isgreater than the pump-error.
 6. The device in accordance with claim 5,wherein the device includes three test-resistors that are selectivelyconnectable between two of the sensor-terminals, wherein the controllercontrols the connection of the test-resistor between the twosensor-terminals.
 7. The device in accordance with claim 6, wherein afirst-test-resistor is not connected between the reference-terminal andthe return-terminal, a second-test-resistor is connected between thereturn-terminal and the pump-terminal, and a third-test-resistor isconnected between the pump-terminal and the tag-terminal.
 8. The devicein accordance with claim 1, wherein the controller determines afifth-value based on a difference between signals at the tag-terminaland the pump-terminal while the current-sink is disconnected, determinesa sixth-value based on the difference between signals at thetag-terminal and the pump-terminal while the current-sink is connectedto the tag-terminal, determines a tag-error based on the differencebetween the sixth-value and the fifth-value, and determines that ashort-circuit is present on the tag-terminal when a tag-threshold isgreater than the tag-error.
 9. The device in accordance with claim 8,wherein the device includes three test-resistors that are selectivelyconnectable between two of the sensor-terminals, wherein the controllercontrols the connection of the test-resistor between the twosensor-terminals.
 10. The device in accordance with claim 9, wherein afirst-test-resistor is not connected between the reference-terminal andthe return-terminal, a second-test-resistor is connected between thereturn-terminal and the pump-terminal, and a third-test-resistor isconnected between the pump-terminal and the tag-terminal.
 11. The devicein accordance with claim 1, wherein the controller determines afirst-value based on a difference between signals at thereference-terminal and the return-terminal while the current-sink isdisconnected, determines a second-value based on the difference betweensignals at the reference-terminal and the return-terminal while thecurrent-sink is connected to the reference-terminal, determines areference-error based on the difference between the second-value and thefirst-value, and determines that a short-circuit is present on thereference-terminal when a reference-threshold is greater than thereference-error, and wherein the controller determines a third-valuebased on the difference between signals at the pump-terminal and thereturn-terminal while the current-sink is disconnected, determines afourth-value based on the difference between signals at thepump-terminal and the return-terminal while the current-sink isconnected to the pump-terminal, determines a pump-error based on thedifference between the fourth-value and the third-value, and determinesthat the short-circuit is present on the pump-terminal when apump-threshold is greater than the pump-error, and wherein thecontroller determines a fifth-value based on the difference betweensignals at the tag-terminal and the pump-terminal while the current-sinkis disconnected, determines a sixth-value based on the differencebetween signals at the tag-terminal and the pump-terminal while thecurrent-sink is connected to the tag-terminal, determines a tag-errorbased on the difference between the sixth-value and the fifth-value, anddetermines that the short-circuit is present on the tag-terminal when atag-threshold is greater than the tag-error, and wherein the controllerdetermines that the short-circuit is present on the return-terminal whenthe reference-error is greater than the reference-threshold and when thepump-error is greater than the pump-threshold and when the tag-error isgreater than the tag-threshold.
 12. The device in accordance with claim11, wherein the device includes three test-resistors that areselectively connectable between two of the sensor-terminals, wherein thecontroller controls the connection of the test-resistor between the twosensor-terminals.
 13. The device in accordance with claim 12, wherein afirst-test-resistor is connected between the reference-terminal and thereturn-terminal, a second-test-resistor is connected between thereturn-terminal and the pump-terminal, and a third-test-resistor isconnected between the pump-terminal and the tag-terminal when thefirst-value and the second-value are determined, and wherein thefirst-test-resistor is not connected between the reference-terminal andthe return-terminal, the second-test-resistor is connected between thereturn-terminal and the pump-terminal, and the third-test-resistor isconnected between the pump-terminal and the tag-terminal when thethird-value, the fourth-value, the fifth-value and the sixth-value aredetermined.